From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>, Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Tejun Heo <tj@kernel.org>,
Calvin Owens <calvinowens@fb.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Peter Hurley <peter@hurleysoftware.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCHv7 4/8] printk: always use deferred printk when flush printk_safe lines
Date: Mon, 6 Feb 2017 10:48:46 +0900 [thread overview]
Message-ID: <20170206014846.GA1750@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20170203111849.GO23754@pathway.suse.cz>
On (02/03/17 12:18), Petr Mladek wrote:
[..]
> > by "the new approved variant" do you mean resend of the entire
> > patch set (v8) or just 0004 patch?
>
> I depends on how many and how complicated are possible conflicts
> with the followup patches.
>
> It is perfectly fine to send just 0004 if there are no conflicts
> or if they are trivial to resolve.
so there are no conflicts at all. 0004 can be replaced with the patch below.
but the thing is - I want to keep printk_safe_flush_line() around.
we call
static void printk_safe_flush_line(const char *text, int len)
{
/*
* Avoid any console drivers calls from here, because we may be
* in NMI or printk_safe context (when in panic). The messages
* must go only into the ring buffer at this stage. Consoles will
* get explicitly called later when a crashdump is not generated.
*/
printk_deferred("%.*s", len, text);
}
from many places:
4x printk_safe_flush_buffer()
1x __printk_safe_flush()
replacing printk_safe_flush_line() with printk_deferred() produces things
like these
printk_deferred("%.*s", end - start, start);
printk_deferred("%.*s", strlen(newline), newline);
which, I think, makes the code worse. any objections?
just in case, the patch (which I prefer to be ignored)
===8<======8<===
>From daa9bd8c2659a91036c00e22bb218be6871a371d Mon Sep 17 00:00:00 2001
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Date: Tue, 27 Dec 2016 23:16:07 +0900
Subject: [PATCH] printk: always use deferred printk when flush printk_safe
lines
Always use printk_deferred() in printk_safe_flush_line().
Flushing can be done from NMI or printk_safe contexts (when
we are in panic), so we can't call console drivers, yet still
want to store the messages in the logbuf buffer. Therefore we
use a deferred printk version.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Suggested-by: Petr Mladek <pmladek@suse.com>
---
kernel/printk/printk_safe.c | 30 ++++++++++++------------------
1 file changed, 12 insertions(+), 18 deletions(-)
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index efc89a4e9df5..801f0f1c7547 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -110,19 +110,6 @@ static int printk_safe_log_store(struct printk_safe_seq_buf *s,
return add;
}
-static void printk_safe_flush_line(const char *text, int len)
-{
- /*
- * The buffers are flushed in NMI only on panic. The messages must
- * go only into the ring buffer at this stage. Consoles will get
- * explicitly called later when a crashdump is not generated.
- */
- if (in_nmi())
- printk_deferred("%.*s", len, text);
- else
- printk("%.*s", len, text);
-}
-
/* printk part of the temporary buffer line by line */
static int printk_safe_flush_buffer(const char *start, size_t len)
{
@@ -136,7 +123,14 @@ static int printk_safe_flush_buffer(const char *start, size_t len)
/* Print line by line. */
while (c < end) {
if (*c == '\n') {
- printk_safe_flush_line(start, c - start + 1);
+ /*
+ * Avoid any console drivers calls from here, because
+ * we may be in NMI or printk_safe context (when in
+ * panic). The messages must go only into the ring
+ * buffer at this stage. Consoles will get explicitly
+ * called later when a crashdump is not generated.
+ */
+ printk_deferred("%.*s", c - start + 1, start);
start = ++c;
header = true;
continue;
@@ -149,7 +143,7 @@ static int printk_safe_flush_buffer(const char *start, size_t len)
continue;
}
- printk_safe_flush_line(start, c - start);
+ printk_deferred("%.*s", c - start, start);
start = c++;
header = true;
continue;
@@ -163,8 +157,8 @@ static int printk_safe_flush_buffer(const char *start, size_t len)
if (start < end && !header) {
static const char newline[] = KERN_CONT "\n";
- printk_safe_flush_line(start, end - start);
- printk_safe_flush_line(newline, strlen(newline));
+ printk_deferred("%.*s", end - start, start);
+ printk_deferred("%.*s", strlen(newline), newline);
}
return len;
@@ -206,7 +200,7 @@ static void __printk_safe_flush(struct irq_work *work)
if ((i && i >= len) || len > sizeof(s->buffer)) {
const char *msg = "printk_safe_flush: internal error\n";
- printk_safe_flush_line(msg, strlen(msg));
+ printk_deferred("%.*s", strlen(msg), msg);
len = 0;
}
--
2.11.1
next prev parent reply other threads:[~2017-02-06 1:48 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-27 14:16 [PATCHv7 0/8] printk: use printk_safe to handle printk() recursive calls Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 1/8] printk: use vprintk_func in vprintk() Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 2/8] printk: rename nmi.c and exported api Sergey Senozhatsky
2017-01-04 13:07 ` Petr Mladek
2017-02-01 15:48 ` Steven Rostedt
2017-02-01 15:50 ` Steven Rostedt
2017-02-23 7:50 ` Geert Uytterhoeven
2017-02-23 8:02 ` Sergey Senozhatsky
2017-02-23 9:23 ` Geert Uytterhoeven
2016-12-27 14:16 ` [PATCHv7 3/8] printk: introduce per-cpu safe_print seq buffer Sergey Senozhatsky
2017-01-04 13:31 ` Petr Mladek
2017-01-05 1:01 ` Sergey Senozhatsky
2017-02-01 15:52 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 4/8] printk: always use deferred printk when flush printk_safe lines Sergey Senozhatsky
2017-02-01 16:06 ` Steven Rostedt
2017-02-02 6:05 ` Sergey Senozhatsky
2017-02-02 15:37 ` Petr Mladek
2017-02-02 15:52 ` Petr Mladek
2017-02-03 2:04 ` Sergey Senozhatsky
2017-02-03 11:18 ` Petr Mladek
2017-02-06 1:48 ` Sergey Senozhatsky [this message]
2017-02-06 2:08 ` Sergey Senozhatsky
2017-02-06 12:16 ` Petr Mladek
2017-02-06 13:27 ` Steven Rostedt
2017-02-06 16:42 ` Sergey Senozhatsky
2017-02-06 16:55 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 5/8] printk: report lost messages in printk safe/nmi contexts Sergey Senozhatsky
2017-01-04 14:46 ` Petr Mladek
2017-01-05 1:01 ` Sergey Senozhatsky
2017-02-01 16:37 ` Steven Rostedt
2017-02-02 2:02 ` Sergey Senozhatsky
2017-02-02 14:34 ` Steven Rostedt
2017-02-02 16:13 ` Petr Mladek
2017-02-03 1:57 ` Sergey Senozhatsky
2017-02-03 3:13 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 6/8] printk: use printk_safe buffers in printk Sergey Senozhatsky
2017-01-31 17:27 ` Ross Zwisler
2017-02-01 9:06 ` Jan Kara
2017-02-01 9:37 ` Peter Zijlstra
2017-02-01 15:39 ` Petr Mladek
2017-02-01 16:15 ` Peter Zijlstra
2017-02-01 16:41 ` Steven Rostedt
2017-02-02 2:11 ` Sergey Senozhatsky
2017-02-02 9:07 ` Peter Zijlstra
2017-02-02 10:03 ` Sergey Senozhatsky
2017-02-02 15:20 ` Petr Mladek
2017-02-03 2:45 ` Sergey Senozhatsky
2017-02-02 1:59 ` Sergey Senozhatsky
2017-02-01 17:04 ` Steven Rostedt
2017-02-02 2:13 ` Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 7/8] printk: remove zap_locks() function Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 8/8] printk: convert the rest to printk-safe Sergey Senozhatsky
2017-01-04 16:28 ` Petr Mladek
2017-01-05 1:00 ` Sergey Senozhatsky
2017-01-05 16:58 ` [PATCHv7 0/8] printk: use printk_safe to handle printk() recursive calls Petr Mladek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170206014846.GA1750@jagdpanzerIV.localdomain \
--to=sergey.senozhatsky.work@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=calvinowens@fb.com \
--cc=jack@suse.cz \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=peter@hurleysoftware.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sergey.senozhatsky@gmail.com \
--cc=tj@kernel.org \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).